From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The unreliability of evaporative cooling systems in engines compared to water-cooled systems, detailing faults and proposed modifications.
| Identifier | ExFiles\Box 178\4\ img071 | |
| Date | 5th May 1932 | |
| ORIGINAL To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to RE. E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Lr.{Mr Ellor} c. to EP.{G. Eric Platford - Chief Quality Engineer} EVAPORATIVE COOLING. 376 Tests on the bench and tests in the air have proved that an engine running under evaporative cooling conditions is very much less reliable than an engine running under water cooled conditions. The faults which develop are all cylinder troubles. The best test we have on the bench is 100 hours Type Test on No.39 engine. At the finish the engine failed to get a certificate because of the difficulty of starting the engine. Investigation tests since then have proved that this difficulty is due to (1) distorted valve seats, (2) Leakage round the back of the valve seats, (3) excessive wear of piston rings, increasing gap. On all the Type Tests we have done on the water cooled engines (12 in all), these faults have never occurred. The best record we have outside on engines flying under evaporatively cooled conditions are the two engines in the Southampton, which ran for 45 Hours without giving trouble, but after that time they only averaged six or seven hours between leaks developing. If we take our standard water cooled engine, there have been any amount of tests to show that this engine can be boosted up to 800 or 900 HP. on the ground and still run satisfactorily. The engine which will run water cooled under these conditions is not satisfactory under evaporatively cooled conditions even at normal powers, until we increase the size of the water pump and increase the size of water outlets. When we have our engine with the larger pump and the larger water outlets we can never approach the power output that we can run under water cooled conditions. This means that 39 Type Test engine which represents the final development we have arrived at so far for evaporative cooling, could never do the Special Category Type Test. There are modified cylinders in hand which allow the steam to get away more easily, which we think will very possibly allow us to get nearer the power of the water cooled job on an evaporatively cooled engine. The patterns for these cylinders are at present being made. | ||